The ACT Government said on Monday it was joining that campaign by "using this image across Government assets in the lead up to Australia Day".

"The image of these young girls is a wonderful example of multiculturalism at work," an ACT Government statement said.

"These girls are proudly Australian but also respectful of their heritage. They are a fine example of a 21st century Australia which should be celebrated and seen by as many people as possible"

There will always be racist rednecks: Barr

Chief Minister Andrew Barr has slammed the reaction to the advertisement as "fanatical" and "irrational", adding the Government would not back down.

"We shouldn't bow to that sort of intimidation," he said.

"There will always be racist rednecks in any community but I'm not going to give them any succour in the ACT.

"If these are serious threats then ... those who've made them should be arrested and the full force of the law thrown at them.

"You can't threaten to blow up buildings in this country without facing criminal charges."

Mr Barr said he was confident the majority of Canberrans supported the billboard.

"For those who are concerned about the contents of the signs I have a very simple message: 'get a life, get over it'," he said.

'I'm shocked something like this would happen in Canberra'

Chair of the Canberra Multicultural Community Forum Diana Abdel-Rahman said the threats were out of character for Canberrans.

"I'm still shocked and I'm shocked that something like this would be happening in Canberra," Ms Abdel-Rahman told ABC Radio Canberra.

"We have a community that pretty much gets on, live and let live more or less you know, we accept everyone.

"We disagree, absolutely, but we don't threaten each other with violence."

She said most of the time the abuse was hypocritical.

"What concerns me is that the same people who are threatening and being abusive about Muslims are the same ones that complain about Muslims not integrating or being part of Australian society," Ms Abdel-Rahman said.

"Sometimes I just think we're damned if we do and damned if we don't."